Mechanism and Specificity of two Restriction Enzymes, CauI and CauII, that Recognize Asymmetrical DNA Sequences

Abstract

Type II restriction endonucleases are enzymes that recognize specific nucleotide sequences on duplex DNA and cleave both strands of the duplex at fixed locations relative to their recognition sites (1). The only co-factor that they need is Mg2+, while type I and Type III restriction enzymes also need ATP and S-adenosyl methionine for maximal activity (2). Type I and type III enzymes also differ from type II by cleaving DNA at variable distances from their recognition sites (2). Hence, the study of type II restriction enzymes was initially motivated by their unique applications in the analysis of DNA and in the construction of recombinant DNA molecules (3). However, these enzymes also provide examples of DNA-protein interactions whose mechanisms are amenable to molecular analysis.